Coupler structure of hand grinder

ABSTRACT

Proposed is a coupler structure of a hand grinder. The coupler structure is fastened to a rotating shaft of a grinder body to enable a machining disc to be more simply and rapidly attached to or detached from the grinder body. Fabrication costs are significantly reduced by simplifying the components associated with the coupler mounted on the rotating shaft of the grinder body. Since the consumable disc is easily attached to and detached from the coupler with one touch, a replacement operation is performed rapidly, thereby significantly improving the efficiency of work.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a U.S. national phase application of PCTInternational Application PCT/KR2021/006541, which claims priority toKorean Patent Application No. 20-2020-0001783, filed on May 27, 2020,the entire contents of which are herein incorporated by reference.

TECHNICAL FIELD

The present invention relates to a coupler structure of a hand grinder,the coupler structure being configured to be fastened to a rotatingshaft of a grinder body and to enable a machining disc to be more simplyand rapidly attached to or detached from the grinder body.

BACKGROUND ART

In general, a hand grinder is used to, for example, smoothly trim arough surface portion or a portion to be painted of a machined componentor cut a portion of a raw material, such as a pipe, an angle iron, or asteel plate. That is, the hand grinder can perform an operation of, forexample, grinding or cutting an insufficiently-machined portion, such asa corner, of a workpiece using a consumable disc by running a rotatingshaft of a grinder body at high speed by driving an electric motor orusing air pressure generated by driving a compressor. The disc may beeasily consumed, since a grindstone or sandpaper wears together with asurface to be ground. Thus, a number of discs must be provided and aused disc must be replaced with a new disc frequently. Accordingly,there has been improvement in a structure for facilitatingattachment/detachment of discs.

Some structures for mounting a disc on such a hand grinder are disclosedin Korean Utility Model Application Publication No. 20-1989-0010365 andKorean Utility Model Application Publication No. 20-1996-0026826. Asdisclosed in these documents, after a disc is fitted around and fixed toa rotating shaft mounted on a grinder body, the disc is fixed using anut or by fastening a bolt to the rotating shaft. Thus, according tothis structure, the disc is fastened to the grinder body simply usingthe bolt or the nut. In this situation, however, fastening force may bereduced by, for example, friction of the disc rotating at high speed orby minute vibrations, thereby causing a worker to be anxious. In fact, aseparate cover is disposed around the disc to prepare for a situation inwhich the disc is loosened and causes an accident.

In addition, Korean Patent Application Publication No. 10-2009-0074461discloses a technology in which a disc holder integrated with a disc maybe fastened by screw engagement by providing a fixing holder on arotating shaft of a grinder body. Thus, the disc may be prevented frombeing loosened from the fixing holder. In addition, the disc may be moreeasily and rapidly attached and detached using a brake unit provided onthe grinder body. According to this structure, the disc holder must befastened to the fixing holder on the rotating shaft by screw engagement.Accordingly, the disc holder must be inconveniently loosened or fastenedagain during work and the separate brake unit must be operated, therebycausing significant difficulty to a worker.

DISCLOSURE Technical Problem

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an objective of thepresent invention is to provide a coupler structure of a hand grinder,wherein the coupler structure mounted on a rotating shaft of a grinderbody is fabricated in a simplified structure enabling a disc to beattached and detached with one touch, thereby improving the efficiencyof work at low cost.

Technical Solution

In order to accomplish the above objective, the present invention mayprovide a coupler structure of a hand grinder. The coupler structure mayinclude: a housing 70 configured to be attached to and detached from arotating shaft 11 of a hand grinder; a top fastening block 80A and abottom fastening block 80B fitted around and fixed to outercircumferential portions of the housing, respectively; and a spring 90situated between the top fastening block and the bottom fastening blockto provide elasticity. The housing 70 may include a cylindrical bodythrough which an inner diameter portion 71 configured to be fittedaround and fixed to the rotating shaft extends, four protrusions 73extending from a top outer circumferential portion of the cylindricalbody at right angles to face each other, and a male thread 74 providedon a bottom outer circumferential portion located below the protrusions.The top fastening block 80A may include four recesses 82 extendingoutward from a central through-hole 81 a such that protrusions 73 arefitted into the recesses 82, respectively, and an outer circumferentialrim 83 a protruding from an outer peripheral portion of the topfastening block. A flange 85 b having a female thread 85 a configured tobe fastened with the male thread 74 may be provided on a disc-shapedbody 84 of the bottom fastening block 80B. The spring 90 may beaccommodated between the outer circumferential rim 83 a provided on theouter peripheral portion of the top fastening block 80A and an outercircumferential portion of the flange 85 b provided on the disc-shapedbody 84 of the bottom fastening block 80B.

Advantageous Effects

According to characteristics of the present disclosure, it is possibleto significantly reduce fabrication costs by simplifying the componentsassociated with the coupler mounted on the rotating shaft of the grinderbody. Since the consumable disc can be easily attached to and detachedfrom the coupler with one touch, a replacement operation can beperformed rapidly, thereby significantly improving the efficiency ofwork.

DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view illustrating components of a handgrinder disclosed in Korean Patent No. 10-0973157;

FIG. 2 is a side view illustrating the hand grinder in which thecomponents are fitted together;

FIGS. 3 and 4 are a cross-sectional view of the disc holder and a bottomview of part “A”;

FIG. 5 is an exploded perspective view of components of the powertransmission unit;

FIGS. 6 and 7 are assembled cross-sectional views of the componentsillustrated in FIG. 5 ;

FIGS. 8 and 9 are plan and views illustrating the operationalrelationship between the stopper and the safety pin of the powertransmission unit;

FIGS. 10 and 11 are plan and bottom views of the housing of the powertransmission unit;

FIG. 12 is an exploded perspective view illustrating a coupler structureof a hand grinder according to the present disclosure;

FIG. 13 is an exploded perspective view illustrating components of thecoupler;

FIGS. 14 and 15 are plan and cross-sectional views of the housing;

FIGS. 16 and 17 are plan and cross-sectional views of the upperfastening pin;

FIGS. 18 and 19 are plan and cross-sectional views of the lowerfastening pin; and

FIG. 20 is a cross-sectional view of the coupler structure mounted onthe grinder body.

BEST MODE

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Itshould be understood, however, that specific structures and functions ofthese embodiments are merely specific examples and the presentdisclosure is not limited thereto.

First, a technology disclosed in Korean Patent No. 10-0973157 will bedescribed in detail as an example to which the present invention isapplied and problems thereof will be discussed, before theconfiguration, as well as functions and effects, of the presentdisclosure are described.

As illustrated in FIGS. 1 to 11 , a hand grinder includes a typicalgrinder body 10, a power transmission unit 20, and a disc holder 30having a disc D mounted integrally therewith.

A rotating shaft 11 having a screw hole 11 a is provided on one frontend of the grinder body 10. The rotating shaft 11 is configured to berotated at high speed by driven by an electric motor or by air pressureof a compressor. The power transmission unit 20 and the disc holder 30are mounted on the rotating shaft 11.

A plurality of recesses 32 is formed on the bottom of a through-hole 31of the disc holder 30, the recesses 32 being spaced apart from eachother at predetermined distances. Three protrusions 33 are providedbetween the recesses 32, thereby allowing the disc holder 30 to bemounted on or detached from the power transmission unit 20.

The power transmission unit 20 includes a stopper 40 and a housing 50rotatable forward and backward on the stopper 40. A cylindrical bindingmember 60 is mounted on the central portion of the housing 50, and isfastened to the rotating shaft 11 of the grinder body 10 using a fixingbolt 12.

A through-hole 41 is provided in the central portion of the stopper 40,and spiral receiving recesses 42 a and 42 b are provided on both sidesof the through-hole 41 so as to be gradually more spaced away from thecenter of the through-hole 41. Concave recesses 43 a and 43 b areprovided between the receiving recesses 42 a and 42 b. A texturedportion 44 is provided on the outer circumferential surface of thestopper 40 to prevent slipping, and a positioning line 44 a is providedon the textured portion 44. Safety keys 46 each including a cylindricalroll 45 a and a quadrangular pawl 45 b are provided in the receivingrecesses 42 a and 42 b, respectively.

The housing 50 is configured to perform a function of locking orunlocking the disc holder 30 by operating the safety keys 46 in thehorizontal direction on the stopper 40. The housing 50 includes a flange51 and a body 52 configured to be fitted into the through-hole 41 of thestopper 40.

A positioning line 51 a is provided on a circumferential surface portionof the flange 51, and quadrangular guide recesses 53 facing each otherare provided on the bottom of the flange 51 such that the quadrangularpawls 45 b on the top portions of the safety keys 46 are fitted into theguide recesses 53, respectively. An insertion recess 54 is provided onthe body 52 below the flange 51 such that the housing 50 fitted into thethrough-hole 41 of the stopper 40 may be bound using a fixing ring 55.Ball plungers 56 are provided on both sides of the top surface of theflange 51, thereby allowing the housing 50 to be more tightly rotated onthe stopper 40.

Each of the ball plungers 56 includes a steel ball 57 and a spring 58inserted into a corresponding one of insertion recesses 51 b provided onboth sides of the top surface of the flange 51, with a fixing screw 59being fastened into the corresponding insertion recess 51 b. In forwardand backward rotation of the housing 50, the ball plungers 56 may beelastically inserted into or removed from the concave recesses 43 a and43 b.

The binding member 60 is fitted into a seating hole 51 c provided in thecentral portion of the housing 50 and fastened to the rotating shaft 11of the grinder body 10. The binding member 60 has a stepped portion 61.Three catching protrusions 62 are provided above the stepped portion 61.(Each of the catching protrusions 62 includes a horizontal portion and avertical portion extending downward from one end of the horizontalportion.) Due to this configuration, the protrusions 33 of the discholder 30 can be fastened and fixed to or detached from the catchingprotrusions 62.

In the hand grinder described above, the disc holder 30 may be attachedto or detached from the rotating shaft of the grinder body 10 in asimple manner. However, the stopper 40 and the housing 50 of the powertransmission unit 20 are provided separately, or the safety keys 46, thesteel balls 57, springs 58, the fixing screws 59 of the ball plungers56, and the like are disposed in a complicated structure. Due to thesefeatures, fabrication costs are increased, thereby causing a significantburden in working sites using a large amount of consumables. Inaddition, impurities, such as fine particles, produced during, forexample, grinding or cutting performed using the hand grinder may causethe operation of the safety keys to be defective and may also cause thegrinder to malfunction.

FIGS. 12 to 20 are views illustrating a coupler structure of a handgrinder according to an embodiment of the present disclosure. Asillustrated in FIGS. 12 to 20 , a coupler K detachably attached to therotating shaft 11 of the hand grinder includes a housing 70, top andbottom fastening blocks 80A and 80B, and a spring 90 situated betweenthe top and bottom fastening blocks 80A and 80B to provide elasticity.

The housing 70 has an inner diameter portion 71 extending therethrough,the inner diameter portion 71 having a thread configured to bescrew-engaged with the rotating shaft 11 of the grinder body 10. Fourprotrusions 73 are provided on the top end portion of the cylindricalbody of the housing 70, each of the protrusions 73 having a catchingstepped portion 72 a. A male thread 74 is provided on the outer portionof the bottom end portion of the housing 70.

In addition, in the top fastening block 80A, four recesses 82 extendoutward from a through-hole 81 a such that the protrusions 73 of thehousing 70 are fitted into the recesses 82, respectively. An outercircumferential rim 83 a protrudes from the outer periphery of the topfastening block 80A. In the bottom fastening block 80B, a flange 85 bhaving a female thread 85 a protrudes from the central portion of adisc-shaped body 84, the female thread 85 a being configured to befastened with the male thread 74 of the housing 70.

Thus, the spring 90 may be accommodated between the top and bottomfastening blocks 80A and 80B. In a position in which the top and bottomfastening blocks 80A and 80B are mounted on the housing 70, individualcomponents may be maintained. In this manner, a disc 100 can be attachedto and detached from the grinder with one touch.

That is, the disc 100 is a consumable intended to be discarded after thelifespan due to use for an extensive period of time. The disc 100typically includes a disc-shaped machining portion 101 configured togrind or cut a workpiece and a holder 102 configured to hold themachining portion 101. Protrusions 103 are provided on the inner portionof the holder 102 such that the disc 100 can be detachably attached tothe housing 70.

According to this configuration, the inner diameter portion 71 of thehousing 70 of the coupler K may be fixed to the rotating shaft 11 of thegrinder body 10 by screw engagement. In this position, when theprotrusions 73 of the housing 70 may be fitted into recesses formed bythe protrusions 103 of the disc 100 and then the disc 100 is rotatedslightly, the protrusions 103 of the disc 100 are fixed by the catchingstepped portion 72a of the protrusions 73.

Here, the top fastening block 80A may be pressed downward while beingelastically repulsed by the spring 90 situated between the top fasteningblock 80A and the bottom fastening block 80B and return to the originalposition, thereby firmly maintain the disc 100.

Thus, it is possible to operate the rotating shaft 11 of the grinderbody 10 at high speed by driving an electric motor or using air pressuregenerated by driving a compressor. At the same time, it is possible toperform an operation of, for example, grinding or cutting aninsufficiently-machined portion, such as a corner, of a workpiece byhigh-speed rotation of the disc 100. In addition, when intended toreplace the disc 100, the disc 100 can be unfastened from the catchingstepped portions 72 a of the protrusions 73 of the housing 70 byslightly rotating the disc 100 in the opposite direction while pressingthe disc 100. In this manner, the disc 100 can be easily detached fromthe housing 70.

The spring 90 may be made from silicone or any other elastic material asan alternative. For example, a cylindrical elastic member made from anelastic material, such as rubber, may be used in place of the spring 90.

As set forth above, according to the coupler structure of the handgrinder according to the present disclosure, it is possible tosignificantly reduce fabrication costs by simplifying the componentsassociated with the coupler mounted on the rotating shaft of the grinderbody. Since the consumable disc can be easily attached to and detachedfrom the coupler with one touch, a replacement operation can beperformed rapidly, thereby significantly improving the efficiency ofwork.

The objective of the present disclosure is realized by the technicalconfiguration described above. Although the present disclosure has beendescribed with respect to the specific embodiments and drawings, thepresent disclosure is not limited thereto. It will be apparent to thoseskilled in the art to which the present disclosure pertains that thepresent disclosure may be variously modified and altered in formswithout departing from the spirit of the present disclosure and thescope of the appended claims and equivalents thereof.

1. A coupler structure of a hand grinder, the coupler structurecomprising: a housing (70) configured to be attached to and detachedfrom a rotating shaft (11) of a hand grinder; a top fastening block(80A) and a bottom fastening block (80B) fitted around and fixed toouter circumferential portions of the housing, respectively; and aspring (90) situated between the top fastening block and the bottomfastening block to provide elasticity, wherein the housing (70)comprises a cylindrical body through which an inner diameter portion(71) configured to be fitted around and fixed to the rotating shaftextends, four protrusions (73) extending from a top outercircumferential portion of the cylindrical body at right angles to faceeach other, and a male thread (74) provided on a bottom outercircumferential portion located below the protrusions, the top fasteningblock (80A) comprises four recesses (82) extending outward from acentral through-hole (81 a) such that protrusions (73) are fitted intothe recesses (82), respectively, and an outer circumferential rim (83 a)protruding from an outer peripheral portion of the top fastening block,a flange (85 b) having a female thread (85 a) configured to be fastenedwith the male thread (74) is provided on a disc-shaped body (84) of thebottom fastening block (80B), and the spring (90) is accommodatedbetween the outer circumferential rim (83 a) provided on the outerperipheral portion of the top fastening block (80A) and an outercircumferential portion of the flange (85 b) provided on the disc-shapedbody (84) of the bottom fastening block (80B).